Abstract

The stereochemically constrained chemotactic peptide analogs, formylmethionyl-\alpha-aminoisobutyrylphenylalanine (formyl-Met-Aib-Phe-OH) and formylmethionylcycloleucinylphenylalanine (formyl-Met-Cyl-Phe-OH) are highly effective in inducing lysosomal enzyme release from rabbit neutrophils. NMR studies of the ${Aib}^2$ analog in ${({CD}_3)}_2SO$ favor a folded conformation in which the Phe NH group is inaccessible to solvent. Intramolecularly hydrogen-bonded conformations involving a Met-Aib-\beta-turn or a \gamma-turn centered at ${Aib}^2$ are considered. The results suggest that folded conformations may allow highly active interactions with the neutrophil formylpeptide receptor.